Aspects of the present disclosure relate generally to wireless communication systems, and more particularly to processing communications related to multiple subscriptions.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
In some wireless networks, a user equipment (UE) can have multiple subscriptions to one or more networks (e.g., by employing multiple subscriber identity module (SIM) cards or otherwise). Such a UE may include, but is not limited to, a dual-SIM, dual standby (DSDS) device. For example, a first subscription may support a first technology standard, such as Wideband Code Division Multiple Access (WCDMA), while a second subscription may be a different subscription to the same technology standard or may support a second technology standard, such as Global System for Mobile Communications (GSM) Enhanced Data rates for GSM Evolution (EDGE) (also referred to as GERAN). Where the UE utilizes a single transceiver to communicate over the multiple subscriptions and/or networks, the UE can tune the transceiver to a given subscription and/or network during a given period of time to communicate therewith, but can only communicate in a single subscription and/or network at a given period of time. As such, when the UE has an active call with the first subscription, the UE may periodically tune away to the second subscription to monitor signals or acquire a connection. During such a tune away mode, the UE loses throughput on the active call with the first subscription due to the inability to receive signals corresponding to the first subscription (e.g., a SUSPEND state). Further, if the tune away mode persists for a relatively long time, then the network managing the active call of the first subscription may determine that the UE is no longer connected due to lack of activity, and thus may terminate the active call of the first subscription.
During a tune away from an active call on a first subscription, the UE may receive a paging signal for initiating a call session on the second subscription. An upper protocol layer (e.g., a radio resource control (RRC) protocol layer) may then commence a connection setup procedure during the tune away period so that the UE may connect to a network using the second subscription, including exchanging of connection messages between the UE and the network. For example, a RRC connection request signal from the UE to the network may provide the UE ID to the network, and an RRC connection setup signal response to the UE may include transport channel information.
To complete the connection setup, the UE may send a RRC connection setup complete signal that includes UE capability information to the second subscription network, so that the network can provide resources to the UE that are compatible with the UE capability. For example, if the UE is enabled to communicate on an enhanced UMTS terrestrial radio access network (E-UTRAN) using high speed and high throughput resources, the UE may send an information element that indicates these capabilities to the network, allowing access to such resources. Subsequently, the UE may receive a downlink direct transfer signal from the second subscription network, from which the caller ID of the second subscription call may be extracted.
In order to maintain voice quality for the active first subscription call session, this connection setup procedure for the second subscription should be kept to as short a duration as possible. Disruption to the active call session may be perceptible to the user when the tune away period is prolonged during the connection setup procedure. One source for a problematic delay is the RRC connection setup complete message generation and transmission when the UE capability information is expansive to include a long list of enhanced capabilities, such as for E-UTRAN resources. For example, when the UE capabilities include E-UTRAN capabilities, the UE may require about 120 protocol data units (PDUs) compared to about 10 PDUs if E-UTRAN capability information is excluded. The impact of transporting these extra PDUs of UE capability information is that the transport duration could be between 2-5 seconds, which would likely be perceptible to the user as a disruption of the active voice call session for this tune away period. With dual receive and single transmit mode of multiple SIM operation, the interruption of a circuit switched (CS) call subscription may be even more severe. Moreover, the UE may be setup to only handle a single SIM call session at a time, and provide an indication of a missed call arriving on the second subscription to the user with the caller ID so that the user may call the caller back after concluding the established call. Hence, the disruption of the active call session for merely extracting the caller ID is bothersome to the user.
Therefore, improvements in the UE capability reporting during a tune away mode are desired.